# Upgrading to Clerk Core 2

In April 2024, we updated Clerk's SDKs to include Core 2. This new core includes:

- 💅 Redesigned and improved component UIs.
- 🔪 The 401 & "flash of white page" that was visible sometimes when syncing auth state was eliminated.
- 🧹 A large number of smaller housekeeping changes, bugfixes, and improvements.
- 📊 [Telemetry](/docs/telemetry) to allow us to better determine feature usage and priority (easy opt-out if you don't like this)

## SDK Guides

Core 2 brings both UI changes and breaking code changes, so each SDK has been updated to a new major version.
We expect upgrades to take less than 30 minutes, and are providing a CLI tool to assist with the process. Please select your SDK below to get started:

- [Next.js](/docs/upgrade-guides/core-2/nextjs)
- [Remix](/docs/upgrade-guides/core-2/remix)
- [Expo](/docs/upgrade-guides/core-2/expo)
- [Node](/docs/upgrade-guides/core-2/node)
- [Fastify](/docs/upgrade-guides/core-2/fastify)
- [React](/docs/upgrade-guides/core-2/react)
- [Backend](/docs/upgrade-guides/core-2/backend)
- [JS](/docs/upgrade-guides/core-2/javascript)
- [Chrome Extension](/docs/upgrade-guides/core-2/chrome-extension)

Note that the `Go`, and `Ruby` SDKs do not yet have a Core 2 release ready - if you are using any of these SDKs there is nothing actionable right now.
